Tennis is a game that tests players’ athleticism, precision and mind. At Wimbledon, however, it’s also a test of players’ underwear.

On Thursday, Austrian junior singles star Jurij Rodionov was sent off the court after officials twice checked his underwear on the court and determined it was too dark to meet the English tournament’s strict all-white dress code.

The two checks took 10 minutes, as officials demanded the 18-year-old lower his waist band to reveal the color of his undergarments. The player was eventually sent off and told to change, before being allowed back on Court 18, where he eventually beat his Australian opponent, Blake Ellis.

Rodionov’s underwear check followed a similar incident on Wednesday that saw officials send off top-seeded junior boys doubles pair Zsombor Piros of Hungary and Wu Yibing of China to change their underpants, too. Officials put them through similar on-court checks before providing the duo with a couple of pairs of tournament-provided white underwear. (For the Win has video of the bizarre incident.) Like Rodionov, Piros and Wu were able to return and beat their opponents.

That players have been told to change their nonwhite undergarments is not new. Wimbledon women’s singles finalist Venus Williams, for instance, was asked to change into a white sports bra after she wore a pink one during her opening match against Elise Mertens. The difference between Williams’s incident and those of the three junior boys, however, is that Williams’s bra straps extended beyond her white jumper and were clearly visible. The junior boys’ underwear, meanwhile, was completely hidden under their tennis shorts, at least according to everyone except Wimbledon officials.

Wimbledon’s dress code, which was last updated in 2014, is so strict that it forbids players from wearing anything nonwhite that can be visible during play, “including due to perspiration.” It’s likely the junior players’ undergarments began to show through their white shorts.

Wimbledon, which has had similar all-white dress codes since the tournament’s inception in 1877, recently justified its strictest dress code to date as a means for leveling the playing field.

“To us, the all-white rule isn’t about fashion, it’s about letting the players and the tennis stand out,” the tournament said in a video it posted about the dress code last week. “Everyone who steps on a Wimbledon court, from a reigning champion through to qualifier does so wearing white. That’s a great leveler. If a player wants to get noticed, they must do so through their play. That’s a tradition we’re proud of.”